Tissue samples, for example samples obtained by biopsies, are typically preserved by deep freezing or by chemical preservation. Deep freezing, for example by liquid nitrogen, maintains the native biomolecular profile of the living tissue, but the formation of ice pellets during the freezing process damages delicate structures in the cells. Thus frozen samples are the preferred mode of preservation when the tissue is kept for future biochemical analysis. Unfortunately, the damage to intracellular structures prevents high quality microscopic analysis of the tissue, for example histo-pathology analysis and immunohistochemical (IHC) analysis. Chemical preservation is typically done by formalin, which cross-links primary amino groups in proteins and thus stabilizes the structure of the tissue. This process kills the cells and degrades many of the biomarkers that are used clinically, including proteins, peptides, DNA, and most notably RNA and its derivatives. Following tissue fixation by formalin the tissue is embedded in paraffin, which enables cutting thin sections (few micron thickness) for high quality microscopy. This process, termed FFPE—formalin-fixed paraffin-embedded—is the most common preservation method of tissue samples for pathology analysis.
Pathologists would like to obtain both the high quality histology that is provided by FFPE and the high quality substrate for biomarker analysis that is provided by frozen sections. However, taking many samples and storing some by cryopreservation and some by FFPE is not the ideal solution since the pathologist is interested in the histology information and the biomarker information from the same location in the tumor. The inhomogeneity of tumors is a well known phenomena, where different properties can be found at different sites in the same tumor. Furthermore, other modes of preservation may be needed—for example preservation that keeps viable cells for future use in cell cultures.
Thus there is a need for a system and a method that will provide the advantages of cryopreservation and of chemo preservation from the same tissue sample, and which would also have the flexibility to apply additional modes of preservation—for example to keep viable cells in the tissue.